Role of Magnetic Resonance Apparent Diffusion Coefficient in Assessment of Solitary Thyroid Nodule

Thyroid nodule is a common lesion of the thyroid gland. Majority of these nodules are benign but have to be distinguished from rare malignant nodules.Clinical examination, Ultrasonography (US), radionuclide scintigraphy, and fine needle aspiration biopsy (FNAB) are the common methods to evaluate thyroid nodules.Routine MRI examination is not sufficient to differentiate benign nodules from malignant ones. DWI has been used in differentiating benign and malignant nodules in thyroid gland. It is a useful noninvasive diagnostic tool in carrying out this differentiation.Our study included 30 patients with with solitary thyroid nodule. All of them underwent US, Color Doppler, conventional MRI and DW-MRI, Histopathological examinations.DW- MRI were performed on all subjects using b values of 500 and 1000 s/mm2 &Mean ADC values of the thyroid nodules were measured at both b values.There is a statistical significant difference between mean ADC values of benign and malignant solitary thyroid nodules. Benign solitary nodules show high ADC value, however malignant solitary nodules show low ADC value with a cut-off value of 1.5 x10-3 mm2/s for the differentiation of benign from malignant thyroid nodules.Finally, we can conclude that, ADC value calculation is a promising method that provides quantitative information in differentiation of malignant solitary thyroid nodules from benign ones. With recommendable b-value 1000 s/mm.